re.match doesn't give error when matches.len is wrong

[timotheecour]

• re.match doesn't give error when matches.len is different from correct number of matches
  this behavior is not documented (actually documentation is vague here): https://nim-lang.github.io/Nim/re.html#findAll.i%2Ccstring%2CRegex%2Cint%2Cint

returns true if s[start..] matches the pattern and the captured substrings in the array matches. If it does not match, nothing is written into matches and false is returned.

• when passing var matches: seq[string] , I would expect re.match to resize matches instead of keeping it empty

Example

import std/re

proc test=
  block:
    var matches: array[2, string]
    if match("abcdefg", re"c(d)ef(g)", matches, 2):
      for s in matches:
        echo s       # => d g

  block:
    # BUG: should give CT (or at least RT) error
    var matches: array[1, string]
    if match("abcdefg", re"c(d)ef(g)", matches, 2):
      for s in matches:
        echo s

  block:
    # BUG: should give CT (or at least RT) error
    var matches: array[3, string]
    if match("abcdefg", re"c(d)ef(g)", matches, 2):
      for s in matches:
        echo s

  block:
    # BUG (or odd design decision): matches doesn't get populated and
    # stays empty; should instead resize accordingly
    var matches: seq[string]
    if match("abcdefg", re"c(d)ef(g)", matches, 2):
      for s in matches:
        echo s
    echo matches

test()

Current Output

d
g

d
g

@[]

Expected Output

CT error (if strings are known at compile time) or RT error

Honestly I'd rather we deprecate re in favor of nre instead of spending time fixing these issues (nre doesn't have that issue); but we should still document bugs until then